contributing/devtool usage: Introduce new topic devtool

* Added new topic devtool in contributing, fixes
  OSTC/OHOS/docs#72 and
  OSTC/planning/core-os#188

* Index.rst modifed to include the new devtool topic.

Signed-off-by: Arul Kumaran <arulkumaran.devarajan@huawei.com>

contributing/devtool.rst

+.. SPDX-FileCopyrightText: Huawei Inc.
+..
+.. SPDX-License-Identifier: CC-BY-4.0
+
+Devtool
+#######
+
+.. contents:: 
+   :depth: 2
+
+`Devtool` is a tool available on OpenEmbedded that allows you to start development
+with your OpenEmbedded distribution. This command tool is available in addition
+to the bitbake command. The `devtool` command is an important component of the
+SDK's extensibility. Run ``devtool --help`` to view the devtool help commands.
+
+This tool commands allows to:
+
+* devtool add: Assists in the development of a new recipe to build a specified source tree.
+* devtool modify: Sets up the build environment to modify the source for an existing recipe.
+* devtool upgrade: Upgrades an existing recipe to a new upstream version.
+
+For more information on using devtool in your sdk workflow, see `Use the Extensible SDK <https://www.yoctoproject.org/docs/3.1.4/mega-manual/mega-manual.html#using-devtool-in-your-sdk-workflow>`_.
+
+Adding a New Recipe
+*******************
+
+To add a new recipe `busybox` to the workspace layer, perform the
+following procedure:
+
+1. Add a new recipe `busybox` to the workspace to build a specified source tree, execute:
+
+  .. code-block:: console
+ 
+     $ devtool add busybox mysources/busybox
+	
+  The above example creates and adds a new recipe named `busybox` to the 
+  workspace layer.
+   
+  .. note::
+
+   The ``devtool add`` command creates the workspace layer when you add a recipe and
+   the workspace layer does not exist.
+   
+2. Edit the source code file and commit the changes to your workspace, execute:
+
+  .. code-block:: console
+ 
+     $ devtool edit-recipe busybox
+	 
+  Executing the above command opens the default editor (as specified by 
+  the editor variable) on the specified recipe.
+   
+3. Build your recipe `busybox` from the workspace, execute:
+
+   .. code-block:: console
+ 
+     $ devtool build busybox
+	
+4. Deploy the recipe `busybox` build output to test on the live target machine, execute:
+
+   .. code-block:: console
+ 
+      $ devtool deploy-target busybox root@<ip of board>
+	  
+5. Populate the workspace layer with your new recipe in the `<WORKSPACE_LAYER_PATH>
+   /workspace/sources` directory.
+
+
+Modifying an Existing Recipe
+****************************
+
+To modify a new recipe `busybox` to the workspace layer, perform the 
+following procedure:
+
+1. Extract the source files for an existing recipe, execute:
+
+  .. code-block:: console
+ 
+     $ devtool modify busybox mysources/busybox
+	 
+2. Edit the code and commit your changes to your local git repository.
+
+   You can use any editor to make the changes and save your source code modifications.
+
+3. Build your recipe `busybox` from the workspace, execute:
+
+   .. code-block:: console
+ 
+     $ devtool build busybox
+
+4. Deploy the recipe `busybox` build output to test on the live target machine, execute:
+
+   .. code-block:: console
+ 
+      $ devtool deploy-target busybox root@<ip of board>
+	  
+ .. note::
+
+   Use command ``devtool undeploy-target busybox root@IP`` to undeploy and edit
+   the recipe source file again.
+   
+5. Apply the changes from the external source tree to a recipe and creates a
+   patch for the committed changes, execute:
+
+   .. code-block:: console
+ 
+      $ devtool update-recipe busybox	  
+	  
+   The above devtool command allows the changes to be exported as patches and adds
+   to the recipe. For more information on patching the source for a recipe, see
+   `Patch the source for a recipe <https://wiki.yoctoproject.org/wiki/TipsAndTricks/Patching_the_source_for_a_recipe>`_.
+	  
+6. Use the devtool reset command to remove a recipe and its configuration
+   from the workspace layer.
+
+ .. code-block:: console
+ 
+    $ devtool reset busybox
+
+Upgrading an Existing Recipe
+****************************
+
+The devtool upgrade command upgrades an existing recipe to that of a more up-to
+-date version found upstream. You can use the devtool upgrade workflow to make
+sure the recipes you are using for builds are up-to-date with their upstream
+counterparts.
+
+To upgrade a new recipe `busybox` to the workspace layer, perform the
+following procedure:
+
+1. Upgrade an existing recipe to a new upstream version, execute:
+
+ .. code-block:: console
+ 
+    $ devtool upgrade busybox
+
+ .. note::
+
+   Execute ``devtool upgrade busybox --version <version to upgrade> --no-patch`` 
+   command to upgrade the recipe to the upstream version without applying patches
+   from the recipe to the new source code.
+  
+2. Push the source code changes or write as patches on top of the recipe, execute:
+
+   .. code-block:: console
+ 
+      $ devtool update-recipe busybox
+	 
+3. Build your recipe `busybox` from the workspace, execute:
+
+   .. code-block:: console
+ 
+     $ devtool build busybox
+
+4. Deploy the recipe `busybox` build output to test on the live target machine, execute:
+
+   .. code-block:: console
+ 
+      $ devtool deploy-target busybox root@<ip of board>
+	  
+ .. note::
+
+   Use command ``devtool undeploy-target busybox root@IP`` to undeploy and edit
+   the recipe source file again.
+   
+5. Check the upgrade status of the recipe `busybox`, execute:
+
+   .. code-block:: console
+ 
+      $ devtool check-upgrade-status -h

contributing/index.rst

@@ -19,3 +19,4 @@ requirements.
    gitlab
    reuse
    dco
+   devtool